There are self-driving techniques for detecting a white line (lane) which is drawn on a road in front of a vehicle or a preceding vehicle in front of the vehicle and controlling the driving direction of the own vehicle based on the detected results. Patent Document 1 has proposed techniques for taking an image of a front area of a vehicle and detecting a white line and a preceding vehicle from the image to control self-driving. Furthermore, as techniques for detecting a preceding vehicle in a taken image, Patent Document 2 has proposed techniques for detecting a preceding vehicle by detecting tail lamps of the preceding vehicle from bright points in the taken image.